7 With the essential tranverse 2-destiny, we have An algorithm of decision for Th 2 (N,<,P) : for Q 1 x 1 Q 2 x 2 F(x 1, x 2 ) The variable x 1 takes its value(s) satisfying F(x 1, x 2 ) on the roots of the trees (all values if Q 1 is universal and at least one value if Q 1 is existential).
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